The present invention relates to a cutting arm on which is stretched on endless component which is driven in rotation by a motor wheel and a return wheel. The arm is provided externally with cutting tools intended to carry out the cutting and demolition of rocks and internally with guide plates which are capable of following a groove provided along said arm.
A cutting arm provided on a rock cutting machine is already known from European Patent No. 0 014 776, which comprises a frame bordered by sliders on the ends of which a driving wheel and a return wheel of an endless component are respectively mounted. This endless component generally consists of a belt externally bearing cutting tools and internally guide plates composed of blocks extending into a groove. In service, the blocks slide over the entire width of the groove on a sheet of fluid provided by means of injectors provided at the bottom of the groove. In the known machines, the sliders are fixed onto the belt by means of screws traversing the belts. The major disadvantage of such fixing is a local weakening of the belt at the points of fixing, since the fixing holes constitute discontinuities which are capable of causing concentrations of tension and bending stresses.
The motor wheel and the return wheel comprises a solid core with a uniform thickness and with a circumferential periphery provided with a rough coating.
In operation, the sliders take support without sliding against the rough coating of the motor wheel in order to drive the belt. To prevent the sliding of the sliders on the motor wheel due to lack of adhesion, it is necessary to stretch the belt as much as possible between the motor wheel and the return wheel. Such a traction pre-stress obviously causes premature wear of the belt.
A cutting arm of a coal cutting machine is also known from German Patent Application DE-A No. 3128264, which comprises an endless belt with a trapezoidal cross-section which is provided externally with diamond cutting components and internally with guide plates. The belt is driven in rotation by a motor wheel and by a return wheel provided with a trapezoidal groove whose inclined walls enclose the sides of the belt.
The belt is provided on its exterior surface with cogs on which are fixedly encased tool-bearing components which are fixed by means of pins engaged in transversal holes.
This configuration allows the full absorption, by means of support surfaces provided for this purpose between the tool head and the tool body, of the considerable shocks to which the tool heads are subjected
It also enables damage of the fixing pins to be prevented in a sure manner.
The major disadvantage of this known cutting arm resides in the fact that the belt is subjected to considerable and repeated flexions at the ends of each of the plates during each passage on the motor and return wheels. These repeated flexions cause localized fatigue of the belt and cause the progressive breakage of same.